1. Field of the Invention
The present invention relates to a microfilm search method and device which searches a desired frame by determining the presence of frames from a density change in microfilm running direction.
2. Description of the Related Art
In a known microfilm search method, search marks (blips) are photographed or recorded besides the frames on microfilm and used as reference marks. The blips of microfilm during running are read and counted, and the blip count is used to identify frame addresses when a specific frame is sought.
On the other hand, there is proposed a search method in which, instead of using the blips, the presence of frames is directly detected, and a desired frame is searched for from a sequence of detected frames. Specifically, a density sensor is disposed within the travel width of the frame, so that the presence of frames is determined from a change in film density detected by the density sensor.
In a case where the presence of frames is detected, end faces of a pair of optical fibers between which a film is placed are opposed to each other. Light incident upon one optical fiber is guided to the film, light transmitted through the film is received by the other optical fiber, and the quantity of received light is detected by a photosensor.
In this case, a plurality of pairs of optical fibers for detecting film densities are disposed in different positions along a film width direction, so that the presence of frames is determined using results detected in the different positions. For example, if frame positions along the film width direction are changed by a change in film photographing system, optical fibers for use may be changed. Moreover, by determining the presence of frames using the film densities detected in a plurality of positions within the frame travel width, determination accuracy can be enhanced.
In a case where the presence of frames is determined in a plurality of positions in the film width direction as aforementioned, frame detection conditions of a plurality of pairs of optical fibers need to be uniform. The frame detection conditions are changed by changes, for example, in quantity of light guided to the plurality of pairs of optical fibers from a light source, attenuation characteristics of the optical fibers, characteristics of photosensor, a threshold value for binarizing an output of the photosensor, and the like. Therefore, these conditions need to be maintained as constant as possible.
If the quantity of light guided to each optical fiber from the light source is not constant, the quantity of light guided into the film becomes non-uniform. Moreover, if a light axis of the each optical fiber for receiving light via the film does not align with a light axis of the corresponding opposed optical fiber for guiding light to the film, the quantity of light reached to the photosensor from the light receiving optical fiber becomes non-uniform. When the quantity of light reaching the photosensor is finally non-uniform, the frame detection accuracy is deteriorated.
As aforementioned, the quantity of light guided to each optical fiber from the light source is preferably constant. However, if each light-guiding optical fiber is separately provided with an independent lamp, it is difficult to keep uniform the quantities of light from all the lamps, and conditions become non-uniform even at the time of lamp replacement. Moreover, the entire device is enlarged. Furthermore, it is proposed that light be radiated to the end face of each optical fiber on the side of the light source from one common lamp. In this case, however, if the optical fibers are once separated from the lamp at the time of inspection or maintenance of the device, the relative positions of the optical fibers will be changed when reassembled. A resultant problem is that the quantity of light incident upon each pair of optical fibers changes, the frame detection conditions also change, and the frame detection accuracy is deteriorated.
On the other hand, in order to equalize the frame detection conditions, the light axes of the end faces of the opposite optical fibers between which the film is placed need to be positioned with high precision.
However, the optical fibers are remarkably fine. For example, the inventor of the present application has studied that, to detect frames of a 16 mm wide microfilm, the film density is detected for each film feeding amount of 0.1 mm. In this case, the diameter of the optical fiber needs to be about 0.5 mm. Therefore, it is requested that the positioning or alignment of the light axes of optical fibers can be performed with high precision and that no mis-alignment is generated in the light axes even after long-time use.
To solve the problem, it is proposed that a pair of optical fiber holding blocks arranged across the film in a width direction are opposed to each other between which the film is placed, so that the optical fibers are held by the blocks. Such construction raises other problems. Specifically, since the film runs through a gap between the blocks at a high speed, the film may be damaged at the time of the high-speed running. Moreover, the end faces of the optical fibers are exposed to the opposite surfaces of the blocks. If the end faces of the optical fibers protrude from the surface of the block, the film running at a high speed directly abuts on the end faces of the optical fibers, and the end faces of the optical fibers are damaged or roughed to lower the light incidence or emission efficiency. If the damaging of the film or the irregular roughing of the optical fiber end faces make non-uniform the light incidence/emission efficiency, the frame detection conditions will be affected, resulting in that the frame detection accuracy further lowers. In an addition, when the film running at a high speed contacts with or rubs surfaces of the blocks, static electricity is generated, and the film is electrically charged to generate electrostatic noises. This also adversely affects the frame detection accuracy.
The present invention has been accomplished in consideration of the circumstances described above, and an object thereof is to provide a microfilm search device in which end faces of a pair of optical fibers are opposed to each other with a film placed therebetween, light incident upon one fiber is guided to the film, light transmitted through the film is received by the other optical fiber, and the presence of frames is detected from a film density change obtained by detecting the quantity of received light with a photosensor, so that the frame detection accuracy can be enhanced.
Another object of the invention is to provide a microfilm search device in which the compactimization of the device is realized, and the quantity of light guided to a plurality of optical fibers is prevented from changing at the time of device disassembly, inspection, maintenance, or the like, so that the frame detection accuracy can be enhanced.
Further object of the invention is to provide a microfilm search device in which a film can run between blocks for holding optical fibers at high speed while preventing damages both of the film and the blocks due to any abut or contact with each other, and in which an electrification of the film is prevented to avoid the generation of electrostatic noises, so that the frame detection accuracy can be prevented from being deteriorated with time.
To attain these and other objects, the present invention provides a microfilm search device for distinguishing presence of frames from a density change in a running direction of a microfilm and searching for a desired frame from the microfilm, comprising:
a first block arranged across the microfilm in a width direction;
a second block arranged across the microfilm in the width direction, end faces of the first and second blocks being opposed to each other with placing the microfilm therebetween;
first optical fibers whose end faces passed through and held by the first block;
second optical fibers whose end faces passed through and held by the second block, the first and second optical fibers are opposed to each other while the microfilm is placed between the end faces in different positions in the film width direction;
a light source for guiding light to said first optical fibers;
a photosensor for detecting a quantity of light incident on said second optical fibers;
a binarizing section for binarizing an output of the photosensor; and
a searching section for determining the presence of frames based on binarized signals to perform frame search;
wherein end portions of said first optical fibers are bunched on the side of said light source, and a bunched portion are detachably and non-rotatably held relative to one lamp incorporated in said light source.
Specifically, in the present invention, one lamp is sufficient as the light source for guiding light to each optical fiber, and the device can be compact as compared with a device in which each optical fiber has a corresponding separate lamp. Moreover, since the position of the end face of each optical fiber of the bunched portion relative to the lamp does not vary after the disassembly, inspection or maintenance of the device, the quantity of light guided to each fiber can maintained at constant or the same, so that the frame detection accuracy can be enhanced.
As the lamp for guiding light to the bunched optical fibers, a lamp as a light source for image projection can be used. Preferably, the bunched portion is inserted through and fixed in a substantially cylindrical plug, and the plug is non-rotatably and detachably attached to a substantially cylindrical socket which is disposed coaxially with a light outlet port or small hole made in a reflection plate surrounding the lamp. The reflection plate has a substantially box shape to surround the lamp. It is also preferred that light from the lamp is prevented from directly entering the optical fibers by placing a shielding plate between the lamp and the small hole.
According to another aspect, the present invention provides a microfilm search device for distinguishing presence of frames from a density change in a running direction of a microfilm and searching for a desired frame from the microfilm, comprising:
a pair of blocks arranged across the microfilm in a width direction and opposed to each other with placing the microfilm therebetween;
a plurality of optical fibers whose end faces passed through and held by the blocks are opposed to each other while the microfilm is placed between the end faces;
a light source for guiding light to the optical fibers held by one block;
a photosensor for detecting a quantity of light incident on the optical fibers held by the other block;
a binarizing section for binarizing an output of the photosensor; and
a searching section for determining the presence of frames based on binarized signals to perform frame search;
wherein each of said blocks is formed of a metal plate exposed to a surface opposite to the microfilm and a resin integrally molded on a back side of the metal plate, and a surface of said metal plate being abraded and polished.
In the aspect, surfaces, which abut on the film, of the metal plates of the blocks for holding the optical fibers whose end faces are opposite to each other with the microfilm being placed therebetween can be smoothed, and provided with a sufficient hardness. There is no possibility of damaging the film. Moreover, since the optical fiber end faces are abraded or burnished together with the metal plate surfaces, the optical fiber end faces do not protrude from the metal plate surfaces and fail to scratch on the film. Therefore, the film is prevented from contacting and damaging the optical fiber end faces, and there is no possibility of deteriorating the light incidence/emission efficiency. Since the metal plate has a conductivity, it is suitable for preventing the film from being electrified.
The metal plate may be of a stainless steel, and the resin may preferably be prepared by mixing glass fiber in polybutylene terephthalate (PBT). In this case, by setting the linear expansion coefficients of the metal plate and the resin substantially the same, the blocks can be prevented from being thermally deformed. When the metal plates of the blocks are electrically connected to each other to the same electric potential, and grounded, the electrification by static electricity and the generation of electrostatic noises can securely be prevented.